Unbalance detection method and washing machine using the same

ABSTRACT

A washing machine and unbalance detection method using the same, which is capable of efficiently detecting unbalance of a rotation tub. A washing machine includes: a washing motor rotating a rotation tub accommodating laundry; a motor velocity detection unit detecting a velocity of the washing motor and outputting a motor velocity signal; and a controller determining whether unbalance of the rotation tub occurs according to an unbalance level determined on the basis of a velocity ripple of the motor velocity signal, and controlling the washing motor according to the determination result. A method of detecting unbalance of a rotation tub accommodating the laundry in a washing machine includes: driving a washing motor in order to rotate the rotation tub; detecting a velocity of the washing motor, and outputting a motor velocity signal; extracting a velocity ripple of the motor velocity signal, the velocity ripple being generated while detecting the velocity of the washing motor; operating the extracted velocity ripple, and detecting an unbalance level; and comparing the detected unbalance level with a reference value, and determining whether the unbalance of the rotation tub occurs.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2005-80800, filed on Aug. 31, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a an unbalance detection method and a washing machine using the same which is capable of efficiently detecting unbalance of a rotation tub.

2. Description of Related Art

A washing machine includes a washing motor for rotating a rotation tub which accommodates laundry. In addition, the washing machine includes a controller for controlling the number of rotating of the washing motor, wherein the controller controls a series of washing operations such as cleaning, rinsing and spin-drying.

FIG. 1 a is a view showing an unbalance state wherein the laundry in a rotation tub has accumulated at one side, and FIG. 1 b is a view showing a balance state wherein the laundry in the rotation tub is evenly arranged.

When spin-drying laundry using centrifugal force generated by rapid rotation of the rotation tub, in the unbalance state where the laundry has accumulated at one side as shown in FIG. 1 a, the rotation tub is excessively shaken so that noise occurs. In order to suppress the occurrence of noise, it is preferred that the spin-dry operation be performed in a balance state wherein the laundry in the rotation tub is evenly arranged as shown in FIG. 1 b.

Aside from the occurrence of noise due to unbalance, there are problems in which spin-drying efficiency is lowered and the laundry is wrinkled, thereby necessitating a need to cope with these problems by detecting the unbalance in the early spin-drying operation.

Meanwhile, the conventional unbalance detection method detects the unbalance based on velocity variation of the motor.

Since the velocity of the motor is instantly varied, it is difficult to detect the degree of velocity variation of the motor. Thus, the conventional unbalance detection method detects the degree of velocity variation of the motor to detect the unbalance in the state where the velocity of the motor kept at a predetermined period of time.

FIG. 2 is a velocity graph of a motor for describing a conventional unbalance detection method.

More particularly, as shown in this drawing, the conventional unbalance detection method increases the angular speed, and performs a clinging operation for causing the laundry to cling to the inside of the rotation tub. Next, the conventional unbalance detection method keeps the angular speed constant during an unbalance detection period of time, detects the amount of velocity variation of the motor, and determines whether the unbalance occurs according to the amount of the unbalance operated on the basis of the detected velocity variation of the motor.

FIG. 3 is a view showing actual velocity of a motor, calculated average velocity and actual average velocity in an unbalance detection period.

In the case where the velocity of the motor during the unbalance detection period of time is low, the laundry in the rotation tub is shifted. For this reason, actual velocity of the motor detected by a velocity sensor is kept constant, and varies as a solid line shown in FIG. 3. In addition, actual average velocity with respect to the velocity of the motor is varied as a dashed line shown in FIG. 3. However, calculated average velocity acquired by averaging the detected velocity of the motor is constant as a one-dot chain line shown in FIG. 3. Accordingly, the velocity variation of the motor is acquired from the calculated average velocity which is different from actual average velocity, and thereby an unbalance determination error may occur.

When the velocity of the motor for applying to the unbalance detection period is high, by keeping the average velocity of the motor constant while the laundry clings to the inside of the rotation tub, reliability of the unbalance determination may be ensured, but in the case where excessive unbalance is detected, the balance state must be returned by iterating clinging operation again, thereby overall spin-drying time may be increased.

BRIEF SUMMARY

Therefore, it is an aspect of the invention to provide a washing machine, wherein, by extracting a velocity ripple component due to unbalance from a motor velocity signal and determining whether the unbalance occurs, it is possible to increase reliability of unbalance determination, and an unbalance detection method using the same.

It is another aspect of the invention to provide a washing machine, wherein, by determining whether the unbalance occurs in real time when driving a washing motor at a predetermined velocity, it is possible to decrease overall spin-drying operation time, and an unbalance detection method using the same.

According to an aspect of the present invention, there is provided a washing machine comprising: a washing motor rotating a rotation tub accommodating laundry; a motor velocity detection unit detecting velocity of the washing motor and outputting a motor velocity signal; and a controller determining whether unbalance of the rotation tub occurs according to an unbalance level determined on the basis of a velocity ripple of the motor velocity signal, and controlling the washing motor according to the determination result.

The controller may determine whether the unbalance of the rotation tub occurs in real time while driving the washing motor.

The controller may determine whether the unbalance of the rotation tub occurs under condition that the velocity of the washing motor varies.

The controller may determine whether the unbalance of the rotation tub occurs under condition that the velocity of the washing motor remains constant.

The controller may further include a high pass filter for detecting the velocity ripple.

The high pass filter may have a cutoff frequency which does not exceed ¼ of an angular speed of the rotation tub.

The controller may include a low pass filter for filtering other components generated according to mechanical characteristics other than an unbalance component, and an absolute value operation unit for detecting an unbalance level according to the unbalance component.

The controller may further include an unbalance determination unit for comparing the unbalance level filtered through the low pass filter with a reference level, and for determining whether the unbalance occurs.

In accordance with yet another aspect of the present invention, there is provided a method of detecting unbalance of a rotation tub accommodating the laundry in a washing machine, the method comprising: driving a washing motor in order to rotate the rotation tub; detecting a velocity of the washing motor, and outputting a motor velocity signal; extracting a velocity ripple of the motor velocity signal, the velocity ripple being generated during detection of the velocity of the washing motor; detecting an unbalance level based of the extracted velocity ripple; and comparing the detected unbalance level with a reference value and determining whether the unbalance of the rotation tub occurs.

The extracting velocity ripple may be performed using a high pass filter with a preset cutoff frequency.

The detecting an unbalance level may include performing operations on an absolute value of the velocity ripple, and filtering other components aside from an unbalance component of the absolute value operated signal using a low pass filter, and wherein other components are generated by mechanical characteristics.

The rotation tub may be rapidly rotated if the resulting determination state indicates a balance state, and an actual spin-dry operation is performed.

The detecting an unbalance level may be simultaneously performed with a clinging operation for causing the laundry to cling to the inside of the rotation tub.

Additional and/or other aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 a is a view showing an unbalance state wherein the laundry in a rotation tub has accumulated at one side, and FIG. 1 b is a view showing a balance state wherein the laundry in the rotation tub is evenly arranged;

FIG. 2 is a velocity graph of a motor for describing a conventional unbalance detection method;

FIG. 3 is a view showing actual velocity of a motor, calculated average velocity and actual average velocity in an unbalance detection period;

FIG. 4 is a schematic block diagram showing the configuration of a washing machine according to an embodiment of the present invention;

FIG. 5 is a detailed block diagram showing the configuration of a controller in FIG. 4;

FIG. 6 is a view showing respective motor velocity signals through a motor velocity detection unit in an unbalance state and a balance state according to an embodiment of the present invention;

FIG. 7 is a view showing respective velocity ripples detected through a velocity ripple detection unit in an unbalance state and a balance state according to an embodiment of the present invention;

FIG. 8 is a view showing respective signals operated through an absolute value operation unit in an unbalance state and a balance state according to an embodiment of the present invention;

FIG. 9 is a view showing respective unbalance levels detected through an unbalance level detection unit in an unbalance state and a balance state according to an embodiment of the present invention; and

FIG. 10 is a flowchart illustrating an unbalance detection method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

FIG. 4 is a schematic block diagram showing the configuration of a washing machine according to an embodiment of the present invention. More particularly, FIG. 4 shows the configuration of a washing machine for driving a washing motor so as to perform a spin-dry operation. However, other known components not shown in FIG. 4 may be employed in order to perform cleaning and rising operations as well as the spin-dry operation.

As shown in this drawing, the washing machine according to an embodiment of the present invention includes: an input unit 10 allowing a user to input operation commands which contain a command for setting a spin-dry operation; a controller 20 for controlling overall operations of the washing machine; a motor driver 30 for driving a washing motor 40 under control of the controller 20; and a motor velocity detection unit 50 for providing a motor velocity signal to the controller 20, wherein the motor velocity signal corresponds to an angular speed of the washing motor 40. Herein, the motor velocity detection unit 50 can be embodied using a hall sensor or an encoder.

FIG. 5 is a detailed block diagram showing the configuration of a controller in FIG. 4.

As shown in this drawing, the controller 20 controls a velocity ripple extraction unit 21, an absolute value operation unit 22, an unbalance level detection unit 23, an unbalance determination unit 24 and a motor control unit 25.

When performing a spin-dry operation after cleaning and rinsing the laundry, the washing motor 40 of FIG. 4 is firstly driven so as to perform a clinging operation for causing the laundry to cling to the inside of the rotation tub. Herein, the laundry in the rotation tub is generally arranged to the unbalance state as shown in FIG. 1 a. If rotation velocity of the washing motor 40 is low, the laundry may move in the rotation tub.

FIG. 6 is a view showing respective motor velocity signals through a motor velocity detection unit in an unbalance state and a balance state according to the present invention.

As shown in this drawing, while varying the velocity of the washing motor 40, the velocity ripple extraction unit 21 extracts velocity ripple (Y2) from the motor velocity signal (Y1) which is provided through the motor velocity detection unit 50. The velocity ripple extraction unit 21 may use a high pass filter (HPF) or a band pass filter (BPF). According to an embodiment of the present invention, the velocity ripple extraction unit 21 may use the high pass filter (HPF) with a predetermined cutoff frequency (Fcutoff-H), wherein the cutoff frequency (Fcutoff-H) is set to a value which does not exceed ¼ of an angular speed (Ftub) of the rotation tub.

FIG. 7 is a view showing respective velocity ripples detected through a velocity ripple detection unit in an unbalance state and a balance state according to the present embodiment of the present invention.

As shown in this drawing, the velocity ripple (Y2) provided to the absolute value operation unit 22 through the velocity ripple extraction unit 21 is a waveform signal in which a direct current (DC) component is removed.

FIG. 8 is a view showing respective signals operated through an absolute value operation unit in an unbalance state and a balance state according to the present embodiment of the present invention

As shown in this drawing, the absolute value operation unit 22 squares the extracted velocity ripple (Y2), Y2*Y2, and provides a waveform signal above 0 (Y3) to the unbalance level detection unit 23.

FIG. 9 is a view showing respective unbalance levels detected through an unbalance level detection unit in an unbalance state and a balance state according to the present embodiment of the present invention.

As shown in this drawing, the unbalance level detection unit 23 removes other components aside from signal components generated by the unbalance, and outputs an unbalance level (Y4) to the unbalance determination unit 24. Herein, other components represent components generated by mechanical characteristics such as a belt and pulley for transmitting power of the motor to the rotation tub. The unbalance level detection unit 23 may use a low pass filter (LPF) with a predetermined frequency (Fcutoff-L).

The unbalance level (Y4) provided through the unbalance level detection unit 23 is provided in consideration of an influence of velocity variation of the washing motor in real time.

The unbalance level detection unit 23 compares the provided unbalance level (Y4) with a predetermined reference value, and determines whether the unbalance occurs. For example, when the unbalance level (Y4) is 0, the unbalance level detection unit 23 recognizes that the resulting determination state is a balance state wherein the laundry in the rotation tub is evenly arranged, and outputs the corresponding unbalance determination signal to the motor control unit 25. Thus, the motor control unit 25 outputs a motor driving signal to a motor driver 30, and rapidly rotates the rotation tub so as to substantially perform the spin-dry operation.

According to an embodiment of the present invention, since the unbalance level is detected from the motor velocity signal while driving the washing motor, the unbalance can be determined in real time. In addition, by extracting the velocity ripple from the motor velocity signal and determining whether the unbalance occurs on the basis of the extracted velocity ripple, it is possible to accurately determine whether the unbalance occurs.

In addition, according to an embodiment of the present invention, with respect to the velocity ripple, by operating the absolute value and filtering using the low pass filter, it is possible to prevent an unbalance determination error due to the mechanical characteristics.

In addition, according to an embodiment of the present invention, by performing the clinging operation while varying the velocity of the motor, and by simultaneously determining whether the unbalance occurs, if it is determined that the resulting determination state is a balance state, the motor control unit rapidly rotates the rotation tub to substantially perform the spin-drying operation, and thereby it is possible to decrease overall spin-drying time.

Now, an unbalance detection method according to an embodiment of the present invention will be described in detail with reference to FIGS. 4 and 10. It is to be understood that the description of the method of FIG. 10 with concurrent reference to FIG. 4 is for ease of explanation only and that the method can be performed by apparatuses having configurations that differ from that of the apparatus of FIG. 4.

FIG. 10 is a flowchart illustrating an unbalance detection method according to an embodiment of the present invention.

To begin with, the controller 20 sets a spin-dry operation mode after cleaning and rinsing (101).

Next, the motor control unit 25 controls the motor driver 30, and drives a drive of the washing motor 40 which is stopped (103).

While driving the washing motor 40, the motor velocity detection unit 50 detects the velocity of the motor, and outputs the corresponding motor velocity signal (Y1) to the controller 20 (105).

The velocity ripple extraction unit 21 of the controller 20 extracts velocity ripple (Y2) with a high frequency from the motor velocity signal (Y1) (107). That is, in order to extract the velocity ripple (Y2), the velocity ripple extraction unit 21 passes the motor velocity signal (Y1) through a high pass filter with a predetermined cutoff frequency (Fcutoff-H) which is set to a value which does not exceed ¼ of the angular speed (Ftub) of the rotation tub, and provides the velocity ripple (Y2) to the absolute value operation unit 22, wherein a DC component of the velocity ripple (Y2) is removed while passing through the high pass filter.

The absolute value operation unit 22 squares the extracted velocity ripple (Y2), Y2*Y2 so that overall signals have values above 0, and provides an absolute value operated signal (Y3) to the unbalance level detection unit 23 (109).

In order to keep a component due to the unbalance and remove other components, the signal (Y3) provided from the unbalance level detection unit 23 passes through the low pass filter (LPF) with a predetermined cutoff frequency (Fcutoff-L), and is delivered to the unbalance determination unit 24, wherein the unbalance level is filtered while passing through the low pass filter (LPF) (111).

The unbalance determination unit 24 compares the provided unbalance level with a predetermined reference value, determines whether the unbalance exists, and provides an unbalance determination signal to the motor control unit 25, wherein the unbalance determination signal is a signal for control the washing motor according to the unbalance determination (113).

When the motor control unit 25 receives the unbalance determination signal indicating a balance state, the motor control unit 25 rapidly rotates the rotation tub to substantially perform the spin-drying operation (115).

The above unbalance detection method according to the present embodiment of the present invention can be applied to the state where the velocity of the motor is varied, wherein the method extracts the velocity ripple from the motor velocity signal and determines whether the unbalance occurs on the basis of the extracted velocity ripple. However, the above unbalance detection method can be equally applied to the state where the velocity of the motor is maintained constant so as to determine whether the unbalance occurs.

That is, the present embodiment of the present invention can determine whether the unbalance occurs by performing the clinging operation while varying the velocity of the motor. In addition, when the clinging operation is finished, the present invention can determine whether the unbalance occurs by operating the velocity ripple in the state where the velocity of the motor is constantly remained.

As is apparent from the above description, the above-described embodiments of the present invention provide a washing machine and an unbalance detection method using the same, wherein, since the unbalance level is detected from the motor velocity signal while driving the washing motor, the unbalance can be determined in real time. In addition, by extracting the velocity ripple from the motor velocity signal and determining whether the unbalance occurs on the basis of the extracted velocity ripple, it is possible to accurately determine whether the unbalance occurs.

In addition, according to the above-described embodiments of the present invention, with respect to the velocity ripple, by operating the absolute value and filtering using the low pass filter, it is possible to an unbalance determination error due to the mechanical characteristics.

In addition, according to the above-described embodiments of the present invention, by performing the clinging operation while varying the velocity of the motor, and by simultaneously determining whether the unbalance occurs, if it is determined that the resulting determination state is a balance state, the motor control unit rapidly rotates the rotation tub to substantially perform the spin-drying operation, and thereby it is possible to decrease overall spin-drying time.

Although embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents. 

1. A washing machine comprising: a washing motor rotating a rotation tub accommodating laundry; a motor velocity detection unit detecting velocity of the washing motor and outputting a motor velocity signal; and a controller determining whether an unbalance of the rotation tub occurs according to an unbalance level determined based on a velocity ripple of the motor velocity signal, and controlling the washing motor according to the determination result.
 2. The washing machine as set forth in claim 1, wherein the controller determines whether the unbalance of the rotation tub occurs in real time while driving the washing motor.
 3. The washing machine as set forth in claim 1, wherein the controller determines whether the unbalance of the rotation tub occurs when the velocity of the washing motor varies.
 4. The washing machine as set forth in claim 1, wherein the controller determines whether the unbalance of the rotation tub occurs when the velocity of the washing motor remains constant.
 5. The washing machine as set forth in claim 1, wherein the controller comprises a high pass filter detecting the velocity ripple.
 6. The washing machine as set forth in claim 5, wherein the high pass filter has a cutoff frequency which does not exceed ¼ of an angular speed of the rotation tub.
 7. The washing machine as set forth in claim 1, wherein the controller comprises: a low pass filter filtering other components generated according to mechanical characteristics other than an unbalance component; and an absolute value operation unit detecting an unbalance level according to the unbalance component.
 8. The washing machine as set forth in claim 7, wherein the controller further comprises an unbalance determination unit comparing the unbalance level filtered through the low pass filter with a reference level, and for determining whether the unbalance occurs.
 9. A method of detecting unbalance of a rotation tub accommodating the laundry in a washing machine, the method comprising; driving a washing motor in order to rotate the rotation tub; detecting a velocity of the washing motor, and outputting a motor velocity signal; extracting a velocity ripple of the motor velocity signal, the velocity ripple being generated during detection of the velocity of the washing motor; detecting an unbalance level on the basis of the extracted velocity ripple, and; and comparing the detected unbalance level with a reference value, and determining whether the unbalance of the rotation tub occurs.
 10. The method as set forth in claim 9, wherein said extracting velocity ripple is performed using a high pass filter with a preset cutoff frequency.
 11. The method as set forth in claim 9, wherein the detecting an unbalance level includes performing operations on an absolute value of the velocity ripple, and filtering components other than an unbalance component of the absolute value operated signal using a low pass filter, wherein other components are generated by mechanical characteristics.
 12. The method as set forth in claim 9, wherein the rotation tub is rapidly rotated when the resulting determination state indicates a balance state, and an actual spin-dry operation is performed.
 13. The method as set forth in claim 9, wherein the detecting an unbalance level is simultaneously performed with a clinging operation for causing the laundry to cling to the inside of the rotation tub.
 14. A method of decreasing a duration of a spin-drying clothes drying operation, comprising: detecting a first velocity of a tub rotating motor rotating a tub and outputting a motor velocity signal; extracting a velocity ripple of the motor velocity signal, the velocity ripple being generated during detection of the velocity of the washing motor; determining an absolute value of the extracted velocity ripple; detecting a level of unbalance from the absolute value of the extracted velocity ripple; comparing the detected unbalance level with a reference value and determining that an unbalance of the tub is not present when the detected unbalance level is less than or equal to the reference level; rotating the tub at a second velocity higher than the first velocity when an unbalance of the tub is not present.
 15. The method as set forth in claim 14, further comprising rotating the tub at the first velocity when an unbalance of the tub is present, wherein the comparing further comprises determining that an unbalance of the tub is present when the detected unbalance level is greater than the reference level. 